Because they save power and are environmentally friendly, high power LEDs have been rapidly developed and have become mainstream for illumination lamps.
Since incandescent lamps are now forbidden by law to be used or fabricated, high power LEDs have become the new generation light source and the development of high power LEDs by manufacturers has actively progressed. Generally, illumination coverage of incandescent lamps is about 300°, illumination coverage of fluorescent lamps is about 260°, and illumination coverage of LED light bulbs is about 120°. Since the currently available LED light bulbs have less illumination coverage, users have a mistaken impression that the LED light bulbs have insufficient illumination. Accordingly, some have proposed solutions to further increase the illumination coverage of the LED light bulbs, such as LED chips bonded onto a plurality of inclined surfaces of a heat sink, so that light emitted from the LED chips can propagate towards different directions and so obtain illumination coverage greater than 290°. However, it is difficult to bond the LED chips onto the inclined surface of a heat sink. In addition, the LED chips are required to be bonded onto two opposite surfaces of the heat sink. Accordingly, the design is disadvantageous to mass production.